The 41-year-old actor plays the south African president in the biopic about his life, 'Mandela: Long Walk to Freedom', but he admits it took him a long time to learn his dialect.

He said: ''I couldn't do it at the beginning and you know why? because I couldn't understand what he's doing to make him talk like that. And it turns out it's his traditional language, Xhosa.

''When he spoke to people he took pauses. Big pauses. Like that. To make sure they understood every word.''

The British star was also concerned about his appearance because he feared he looked nothing like Mandela - who passed away last Thursday (05.12.13) after his long battle with ill-health - but the director Justin Chadwick was convinced Elba was the right person for the film.

Speaking to the Daily Telegraph newspaper, he explained: ''My worry was I don't look like Mandela. Justin just said, 'Don't worry about it'. But I was saying, 'No one is going to believe me. I am too dark-skinned'. Justin was like, 'It's the presence we want.'''